Last fall, the scientific community went into a minor frenzy. A hunk of interstellar material had been sucked into the Earth’s gravitational field, and was now orbiting the planet.
What was it? Teddy Kareta, a postdoctoral associate at the Lowell Observatory in Flagstaff, was determined to find out.
Kareta joined The Show to discuss how studying this mysterious object was a rare and, in his opinion, precious opportunity.
Full conversation
TEDDY KARETA: Objects that get this close to the Earth are really, really rare. And it's not so often that these things stick around for not just days or weeks, but months. It was sort of an interesting and exciting time.
SAM DINGMAN: And how big was this asteroid?
KARETA: Thirty to 40 feet across. So, not so big that if it were to impact the Earth, we'd be, you know, thinking about "Armageddon" or "Deep Impact," right, movies from the '90s, right? But big enough that, you know, we found it well before it got close to the Earth, and we were able to track it for quite a while afterwards.
DINGMAN: And when you started tracking it, was there anything unique or or remarkable about it?
KARETA: So I mentioned earlier that it's kind of hard for asteroids to get into orbits similar to the Earth, right? So we had to think about what other scenarios might put rocks this close by. One of them is that we could have found space junk. So think, like the Apollo missions from the '50s, we left a lot of rocket parts up in space. That was one scenario we were worried about, or at least wanted to look into, and the other one, which I think we'd been excited about for a long time, but we've been looking, without success, was looking to see whether or not it could be ejected from the moon.
So we got observations of this particular space rock, 2024 PT, ... telescopes, both here in Arizona, up near Flagstaff, as well as in Hawaii, to try to figure out what this thing is made out of. And we quickly realized this doesn't look like paint. It doesn't look like metal. It's not lost space junk. And as we looked at the data in a little bit more detail, we started realizing that it didn't really look like any of the known asteroids, either. So this mini moon, we started to think was a picture, you know, a piece of the real moon.
DINGMAN: Well, this is something that you have a particular interest in, right? Is smaller bodies of the solar system, which would include things like hunks of moon, asteroids, comets. What's interesting to you about studying these, these particular space phenomena?
KARETA: You know, I think when people think about, you know, astronomers studying the solar system, they think about Jupiter, they think about Pluto, they think about stuff that is pretty big in the grand scheme of things, right? But the vast majority of objects in the solar system are what we call the small bodies, the comets, the asteroids. There are always going to be more of those objects to study with telescopes, with computer models, with laboratory work, than we'll ever get visited by spacecraft, right.
As a result, if there are a million and a half known asteroids, and we've seen maybe five to 10 with spacecraft, that's millions of objects left on the table that might have really interesting stories to tell. At the same time, you know, for all the asteroids that get lucky enough to get visited by spacecraft, for all the comets lucky enough to get visited by spacecraft, you're still going to need to compare them to the hundreds or thousands of bodies you've studied with telescopes and in other ways, just because that's the only context you have, right?
DINGMAN: So if I'm hearing you right, there's kind of two factors here. One is the possibility of discovering something on a small body like this that has an interesting story to tell, but also just building out the base of knowledge for comparison for studies of other bodies that will eventually be looked at.
Can you give me an example of either this particular mini moon or another small body that you've studied? Of one of those interesting stories that surprised you?
KARETA: Sure, back in 2019 the second interstellar object was discovered. Interstellar object is the sort of category, the name of the category for comets and asteroids that were formed around other stars. You know, you might have heard of exoplanets, planets around other stars. These are the small bodies of those solar systems. They get thrown out every once in a while, and so far, we've found two as they pass through our own solar system on their way somewhere else. You get a few months to study them, and it's over forever.
In a lot of ways, it's kind of the study of small bodies in the solar system in hard mode. Because we hadn't found any of these objects yet. We didn't know what the interesting questions were to ask, right? We hope that given this once in a lifetime opportunity to study this object before it went away, we hope we measured the stuff that matters, right? Yeah, and I don't think it took maybe three weeks before another paper came out that more or less showed that conclusively, we had no idea what we were measuring. And I think there are people who would find that kind of frustrating, but we learned a lot more about how in the future. We know the better questions to ask next time, do better. It feels iterative, but in a sort of hopeful and encouraging way.
DINGMAN: Yeah, I do find that idea just personally very compelling, that the goal here is not ultimate answers, because we are never going to get the ultimate answers. It's fewer questions tomorrow or smarter questions tomorrow?
KARETA: Yeah, exactly. You know, compared to 30 years ago, where it was a handful of groups in a handful of countries hunting for potentially dangerous space rocks, comets, these sorts of things, it's now a real international effort with tons and tons of people involved, really smart people working really long hours to try to keep the earth as safe as possible, right? There's still going to be, you know, rocks worth worrying about, comets worth worrying about, but it's a really tremendous large group of smart people working, you know, day and very much night to keep everyone safe, right? You know, that should make you feel good.
DINGMAN: Yeah. Have you ever seen anything in your research that gave you even a flicker of a scare about some kind of "Deep Impact" or "Armageddon" scenario, or is the possibility of that so remote that it's not even worth thinking about?
KARETA: I think the scientists who work on this problem regularly have kind of just learned to accept that, yeah, at any given time, there's a few things worth keeping an eye on, but on a day to day basis, I'm not struggling to fall asleep or anything. One thing that was really exciting in this sort of area is a couple of years ago, I was really involved in the Dart spacecraft, the double asteroid redirection test.
We were exactly trying to test what they do in the movies, right? Can you push an asteroid away onto a trajectory where it doesn't hit the Earth, and within a couple of minutes of us hitting the moon of this one asteroid, we already had an idea that, okay, this technique really works in a pinch. This is something that's in our tool kit.
DINGMAN: Yeah.
KARETA: Yeah, you know, I'd rather that we never have to deflect an asteroid. I'd rather we didn't have to worry about it at all. But I'd also like to know if the techniques we have that could be tried work, right? And, you know, I don't want to be at the last minute, you know, giving the president the big button where you could, like, joystick the missile towards the asteroid, right? I'd rather we just knew exactly what to do in what order. And that means you have to test this stuff ahead of time.
DINGMAN: Yeah.
KARETA: You know, I think even the scientists who worry about this on a day to day basis, knowing that something like Dart would work, knowing that we're getting better at hunting for these potentially dangerous objects out in space, both of those are really good news for everybody.
